Device for removing and disposing a stack of flat products

ABSTRACT

The invention concerns a method for removing and disposing a stack of flat products from a stacking device into a bundling device, in particular, in a folding box manufacturing machine, wherein the stack is grasped in the stacking device by a gripper mounted to a robot arm, and is disposed in the bundling device, wherein the first stack grasped by the gripper and/or the subsequent second stack is/are rotated before being disposed in the bundling device.

This application is a continuation in part of Ser. No. 11/129,407 filed on May 16, 2005 the entire disclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The invention concerns a device for removing a stack of flat products, in particular, of folding boxes, from a stacking device and disposing it in a bundling device, in particular, in a folding box manufacturing machine, wherein the stack, in the stacking device, is grasped by a gripper mounted to a robot arm, and is disposed in the bundling device.

DE 100 13 417 A1 discloses a method and a device for palletizing cardboard boxes. The cardboard boxes are thereby lifted off a transport means by a gripper which is mounted to a robot arm and are disposed on a bundling station. The robot is positioned between the transport means and the bundling station, and the robot arm is pivoted through 180° after grasping the pile to place the grasped stack on the bundling station. The bundling station comprises a Doppler station for grasping, lifting, and turning the deposited stack and optionally placing it onto another stack. It has turned out that a means of this type not only has a complex construction but also operates relatively slowly such that the stacks supplied by the robot arm cannot be conveyed as quickly as would be required by the material flow.

It is therefore the underlying purpose of the invention to further develop a device of the above-mentioned type such that high production speeds can be obtained.

SUMMARY OF THE INVENTION

This object is achieved in accordance with the invention by a device of the above-mentioned type in that a first stack grasped by the gripper and/or a subsequent second stack are turned as well as pivoted before being placed in the bundling device.

The inventive device has the essential advantage that the stacks are already oriented upon disposal in a manner which is required for further transport or for further processing e.g. tying up. The stack disposed by the robot arm must not subsequently be grasped and/or be turned by an additional unit to move it into the desired position. This not only increases the transport speed but also protects the product stack since it must be grasped less frequently, and therefore reduces mechanical interactions on the surface of the stacked, flat products.

In accordance with the invention, all stacks deposited by the gripper can be turned into a respective desired direction. However, rotation may also be restricted to only certain selected stacks.

In a further development, a subsequent stack is disposed onto a previously deposited stack, thereby forming higher stacks which then can be removed by the gripper e.g. from a stack shaft. In this variant, the previously deposited stacks need not be grasped and re-stacked. Stacking is already effected by the gripper such that the stack formed from several stacks can be further transported to be tied up without requiring further handling such as pivoting, stacking etc.

In a preferred method step, the first stack is rotated through +90° and the second stack is rotated through −90°. Alternatively, only the second stack is rotated through 180°. In this manner, the second stacks can be rotated through 180° relative to the first stack and disposed thereon. The stack produced in this fashion has the advantage that even when the flat products are not uniform, e.g. have a thick or high longitudinal side and a thin longitudinal side, such that the stacks have the shape of a prism instead of a cube, they have a substantially uniform and generally cuboid shape and can be immediately packaged after tying up.

They are preferably removed, turned and disposed in parallel planes, i.e. the stack is rotated about a vertical axis. In this manner, large and also heavy piles can be transported to the bundling device, thereby preventing the flat products, which form the stack, from being displaced and also avoiding exertion of excessive moments on the gripper.

In a further development, the second stack is rotated about a horizontal axis. The upper side of the stack is thereby turned downwards before being disposed in the bundling device. Sensitive surfaces of the flat products can e.g. thereby be turned inwards for protection.

In accordance with the invention, the stacking device has two removal planes for the stacks and the gripper removes the stacks from both removal planes. In one removal plane, a stack is formed by downward stacking and in the other removal plane a stack is formed by upward stacking, wherein both stacks are grasped by the gripper and can be disposed at the provided location in the bundling device. Separate gripping devices for upward and downward piled stacks are thereby required.

In accordance with the invention, during transport of the stack from the stacking device to the bundling device, the gripper performs a pivoting motion through an angle which is different from 180°. The stacking device and the bundling device need not be disposed in a straight line, one behind the other, rather can be arranged at an angle with respect to each other or be offset from each other. They may also be parallel and next to each other such that the gripper disposes the grasped pile parallel to the longitudinal axis of the stacking device. In this manner, the overall length of the production plant can be reduced.

The robot arm preferably receives a gripper which is adapted to the format of the folding box, wherein the respective gripper is disposed in a special magazine, thereby minimizing the set-up time.

Further advantages, features and details of the invention can be extracted from the following description which illustrates a preferred device with reference to the drawing. The features shown in the drawing and in the claims and description may be essential to the invention either individually or in arbitrary combination.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a plan view of a device for performing the inventive method;

FIG. 2 shows a side view of the device;

FIG. 3 shows a view of the gripper fork in the direction of the arrow III in accordance with FIG. 2;

FIG. 4 schematically illustrates a method for transporting L-shaped folded boxes; and

FIG. 5 schematically shows rotation of the L-shaped folded boxes to achieve a substantially cuboid, combined folded box stack.

FIG. 1 shows the end of a supply unit, designated by reference numeral 10, which comprises a stacking device 12. An offset robot 14 is disposed downstream of this supply unit 10 and a bundling device, designated in total with 16, is arranged downstream of the offset robot 14. Individual, flat products 17 (FIG. 2), in particular, folding boxes 19, are supplied in the supply unit 10 and are piled up to form a stack 21 in the stacking device 12. When this stack 21 has the required number of folding boxes 19, it is grasped by a gripper 18 which is mounted to the end of a robot arm 20. Through pivoting the robot arm 20 about a vertical axis 22 of the robot 14 and via downward displacement of the gripper 18, the grasped stack 21 can be disposed on a disposing table 24 of a bundling device 16.

It should be emphasized that the stack 21 located in the stacking device 12 can be grasped by the gripper 18 irrespective of where it is stacked. If the folding boxes 19 are downwardly stacked, the finished stack 21 is provided in a lower region of the stacking device 12 to be dispatched, whereas a finished stack 21 which is stacked towards the top must be grasped in an upper region by the gripper 18. For grasping the stack 21, two prongs 26 of a gripper fork 28 underride the stack 21, and a holding-down device 30 is pressed onto the upper side of the stack 21. The stack 21 is thereby safely held such that the individual flat products 17 are not displaced during transport from the stacking device 12 to the bundling device 16. This is also ensured when the stack has a prismatic rather than a cuboid shape, in particular, for stacks of flat products 17 which have a substantially wedge-shaped cross-section with a thicker and a thinner end.

As is shown in FIG. 3, the separation between the two prongs 26 can be adjusted by a handwheel 32 and the separation between the clamp 30 and the prongs 26 can be adjusted using a handwheel 34. In this manner, the gripper fork 28 can be easily adjusted to the shape of the stack 21 to be grasped. To grasp stacks 21 having completely different shapes, the gripper fork 28 can be replaced by a different gripper fork using a quick coupling 36. FIG. 3 also shows that a drive 38 is provided to rotate the gripping fork 28 about a vertical axis 40.

The finished stack 21 in the stacking device 12 is grasped and then supplied to the disposing table 24 through pivoting the robot arm 20. The gripping fork 28 is moreover rotated through +90° or −90° such that the stack 21 held by the gripper fork 28 is either oriented in accordance with arrow 42 or arrow 44. The stack 21 can then either be disposed directly on the disposing table 24 or on a previously deposited stack 21. This has the essential advantage that for prism-shaped stacks 21, a substantially cuboid stack can be formed through stacking two stacks 21 and can subsequently be transported from the disposing table 24 to a bundling station 46 in which a packet cord is tied around the stack.

It is, however, also feasible to position the first stack 21 on the disposing table 24 without turning it about the vertical axis 40, wherein the second stack 21 is then disposed on the first stack 21 after rotation through 180°.

In a further variant, the gripper fork 28 can be rotated about an axis which is orthogonal to the plane of the drawing of FIG. 3 such that the grasped stack 21 can be disposed on the disposing table 24 or on a previously deposited stack 21 with its upper side facing downwards.

In FIG. 1, the stacking device 12 and the bundling device 18 are laterally offset but disposed behind each other with parallel axes. The stacking device 12 and the bundling device 16 may subtend an angle which may be different from 90°. The stacking device 12 and the bundling device 16 may also be disposed parallel and next to each other such that the product flow in the bundling device 16 extends opposite to the product flow in the stacking device 12. Suitable placement of the robot 14 at the end of the supply unit 10 or in the region of the stacking device 12 facilitates supply of the stacks 21 which are removed from the stacking device 12 to the bundling device 16 within the cycle time predetermined by the stacking device 12 to preclude inoperative times within the stacking device 12.

The inventive method also permits forming stacks of prism-shaped stacks 21 without having to re-grasp and relocate the individual stacks 21 after disposal by the robot arm 20. As soon as the required number of stacks 21 has been piled on top of another, the finished stack can be bound in the bundling station 46.

FIG. 4 schematically indicates a manner in which L-shaped planar folded boxes 17 (which are not erected yet) are transported by a transporting device 10. The L-shaped folded boxes have a base portion 50, 52 which comprises two flattened, opposite sides having an elongated portion 50 and a shorter, end portion 52 for the box which is subsequently erected from the folded box structure shown. The dotted line 54 indicates a fold line between the end portion 52 and the elongated portion 50 of the box in the flattened state. The other side of the box with the corresponding end and side portions lies directly beneath the side indicated by references 52 and 50 in FIG. 4. The combined, flattened and folded structure consisting of the base portions 50 and 52 of the two opposite sides are disposed directly on top of each other thereby constituting two plies for the base portion 50, 52 of the L-shaped folded box. Dotted lines 56 indicate flaps corresponding to the bottom portion of the box which are generally folded in an inward manner and lie between the two side portions. The base of the L-shaped folded box therefore has a plurality of plies. Reference symbol FIG. 58 indicates a lid portion of the box extending from one of the end portions 52 in a substantially perpendicular direction and is structured to be folded onto the constructed box portion after erection thereof making use of folding line 57. The lid portion 58 is therefore substantially single plied and consequently much thinner than the multiple ply structure of the base portions 50 and 52. When transporting the box through the transporting means 10 for subsequent stacking and bundling, it is therefore necessary to have the lid portion 58 of the box extend towards the rear, since rapid transport would otherwise lead to lifting of the lid portion 58 and obstruction of the transport process.

FIG. 5 illustrates a rotation scheme for the products in accordance with the invention. A plurality of boxes 17 are transported to a stack having e.g. five to ten folded boxes in the orientation that they had during transport along the transport means 10 illustrated in FIG. 4. This partial stack is then rotated in accordance with FIG. 5 through an angle of plus 90 degrees such that the lid portion faces to the left. A number of subsequently transported and stacked folded boxes are then rotated through an angle of minus 90 degrees before being placed on top of the previous stack of L-shaped folded boxes. In this fashion, the lid 58 and base portions 52, 50 alternately extend towards the left and right in the combined stack. Due to the geometry and symmetry of this rotation process, the resulting combined stack consisting of the alternately stacked folding boxes or groups of folding boxes is substantially cuboid rather than prismatic in shape. This leads to more a stable stack for the folding products and simplifies bundling thereof. 

1. A method for transporting, stacking and removing L-shaped folded boxes and for disposing a stack of L-shaped folded boxes in a bundling mechanism for use in a folding box manufacturing machine, the L-shaped folded boxes having a thicker base portion and a thinner lid portion extending at right angles to the base portion, the method comprising the steps of: a) transporting the L-shaped folded boxes with the base portion leading in a transport direction and the lid portion trailing; b) stacking a number of the L-shaped folded boxes; c) grasping the stack of folded boxes generated in step b) using a robot arm having a gripping means; d) rotating said robot arm and said gripping means through an angle; e) depositing said stack of folded boxes in a bundling device; and f) repeating steps a) through e) while maintaining an orientation of the folded boxes in steps a) through c) and changing an orientation of the stack of folded boxes in steps d) and e) to create a substantially cuboid combined stack of folded boxes.
 2. The method of claim 1, wherein step d) comprises the step of rotating a first stack of folded boxes through an angle of plus 90 degrees with respect to a vertical and subsequently rotating a second stack of folded boxes through an angle of minus 90 degrees with respect to the vertical.
 3. The method of claim 1, wherein step d) comprises the step of rotating a first stack of folded products through a first angle with respect to vertical and subsequently rotating a second stack of folded boxes through a second angle with respect to the vertical, wherein the second angle differs from the first angle by 180 degrees.
 4. The method of claim 1, wherein removal, rotation and disposal are effected in parallel planes.
 5. The method of claim 1, wherein the stack is rotated about a horizontal axis.
 6. The method of claim 1, wherein, in step b), the folded boxes are stacked in two removal planes.
 7. The method of claim 1, wherein, during step d), the robot arm pivots through an angle which differs from 180 degrees.
 8. The method of claim 1, wherein the gripper means disposes the grasped stack in the bundling device parallel to a longitudinal axis of a stacking device or next to a stacking device.
 9. The method of claim 1, wherein the robot arm receives the gripping means, the gripping means being adjusted to a format of the folded boxes.
 10. A device for transporting, stacking and removing L-shaped folded boxes and for disposing a stack of L-shaped folded boxes in a bundling mechanism for use in a folding box manufacturing machine, the L-shaped folded boxes having a thicker base portion and a thinner lid portion extending at right angles to the base portion, the device comprising: means for transporting the L-shaped folded boxes with the base portion leading in a transport direction and the lid portion trailing; means for stacking a number of the L-shaped folded boxes; means for grasping the stacked number of folded boxes using a robot arm having a gripping means; means for rotating said robot arm and said gripping means through an angle; means for depositing said stack of folded boxes in a bundling device; and means for alternately changing an orientation of the stack of folded boxes during deposition thereof to create a substantially cuboid combined stack of folded boxes.
 11. The device of claim 10, wherein a first stack of folded boxes is rotated through an angle of plus 90 degrees with respect to a vertical and a second stack of folded boxes is rotated through an angle of minus 90 degrees with respect to the vertical and disposed upon said first stack of folded boxes.
 12. The device of claim 10, wherein a first stack of folded products is rotated through a first angle with respect to vertical and a second stack of folded boxes is subsequently rotated through a second angle with respect to the vertical and disposed upon said first stack of folded boxes, wherein the second angle differs from the first angle by 180 degrees.
 13. The device of claim 10, wherein removal, rotation and disposal are effected in parallel planes.
 14. The device of claim 10, wherein the stack is rotated about a horizontal axis.
 15. The device of claim 10, wherein the folded boxes are stacked in two removal planes.
 16. The device of claim 10, wherein the robot arm pivots through an angle which differs from 180 degrees.
 17. The device of claim 10, wherein the gripper means disposes the grasped stack in the bundling device parallel to a longitudinal axis of a stacking device or next to a stacking device.
 18. The device of claim 10, wherein the robot arm receives the gripping means, the gripping means being adjusted to a format of the folded boxes. 